Several UI content fixes

This will fix the following trello cards: 

https://trello.com/c/2Ak7AT8k/726-change-default-wording-for-work-category-and-type
https://trello.com/c/4wNobzeN/725-manage-clients-ftl-translate-placeholder-text
https://trello.com/c/x7nKLry6/731-language-cannot-be-empty-warning-on-works-stays-even-after-the-language-field-is-filled-out